This invention relates to novel polysaccharide graft copolymers which contain a reactive aminoethyl halide group and to the method for their preparation. It also relates to the use of the aminoethyl halide-containing graft copolymers as strength agents in paper.
Graft copolymers of polysaccharides such as starches, cellulose and gums are well known in the literature. Various graft copolymers and the methods of preparation are disclosed in "Starch: Chemistry and Technology", second edition, edited by R. L. Whistler et al., Academic Press, Inc., 1984, pp. 403-410 and "Handbook of Water-Soluble Gums and Resins", edited by R. L. Davidson, McGraw-Hill Book Co., 1980, chapter 22, pp. 22-47 to 22-54.
Methods of preparing graft copolymers include polymerizations in water, in water-solvent mixtures and in the dry state, and may be initiated by mechanical, chemical and irradiative techniques. Such methods are typically disclosed in U.S. Pat. Nos. 3,809,664; 3,976,552; 4,131,576; 4,330,443 and 4,690,996.
Some of the monomers which have been used to prepare graft copolymers include acrylic monomers disclosed in U.S. Pat. No. 4,330,443; water soluble monomers such as acrylamide disclosed in U.S. Pat. No. 4,131,576; cationic monomers such as N, N-diallyl-N, N-dialkyl ammonium halides and other salts disclosed in U.S. Pat. Nos. 4,464,523 and 4,737,156 and cationic copolymers of N, N'-methylenebisacrylamide and polyamines disclosed in U.S. Pat. No. 4,278,573.
It is an object of this invention to provide a polysaccharide graft copolymer which contains a reactive aminoethyl halide group that is available for later or post-reaction and thus useful in many applications such as additives in papermaking wherein they provide improved retention and strength properties.